Combined glow cathode and acceleration diaphragm



Jan. 24, 1939. E. TRESCHAU 2,144,998

COMBINED GLOW CATHODE AND ACCELERATTON DTAPHRAGM Filed Sept. 23, 1936 INVENTOR Patented Jan. 24, 1939 COMBINED GLOW CATHODE AND ACCELER- ATION DIAPHRAGM Edwin Treschau, Berlin-Reinickendorf, Germany,

assignor to Allgemeine Elektricitats-Gesellschaft, Berlin, Germany Application September 23, 1936, Serial No. 102,095 In Germany September 24, 1935 8 Claims. (Cl. 250-27) The Braun high-vacuum tube presents, in comparison to. the gas-filled tube, besides important advantages, such as the absolute absence of inertia of the ray and the good linearity of the scale, also a perceptible disadvantage consisting of a lower intensity of the luminous spot. In order to attain equal brightness it would, therefore, in conventional high-vacuum cathode ray tubes, be necessary to make use of higher anode or accelerating voltages, which would also necessitate an increase in the deflecting voltages or deflecting currents for the complete deflection of the beam across the luminous screen. This procedure necessitates, therefore, not only a considerable amount of additional means suitable for the purpose in View, but entails also a more complex system and the use of elements of higher voltage ratings.

Now, according to this invention, the reduction of the beam intensity of high-vacuum tubes, as due to the absence of the positive space charge in front of the cathode, is obviated by arranging upon the cathode, with the aid of a heat-proof body, a} space-charging diaphragm charged positively relatively to the cathode. It is, with this arrangement, not necessary to provide a separate voltage supply to this space-charging diaphragm, the drop of potential of the glowing wire or cathode heater can be used to render the diaphragm sufficiently positive relatively to the cathode. The requisite positive potential of the space-charging diaphragm can be produced also by making it of a material possessing a suitable contact-potential difference relatively to the material of the cathode. The cathode and the spacecharging diaphragm should, as regards their shape and size, be so designed that a collective or focusing eifect is attained so as to cause, if possible, all escaping electrons to take their way through the aperture of the diaphragm that is reproduced upon the screen in the form of a luminous spot of high intensity by means of a suitable electronic-optical system.

The eifect to concentrate as many electrons as possible upon the aperture of the diaphragm can be assisted by the magnetic field produced by a thick-wire coil through which the heating current passes and which because of its size as compared to the cathode heater wire, is not heated to a high temperature. The fluctuation of intensity arising when heating with alternating current can be utilized advantageously, when making use of the arrangement constituting the present invention, for investigating phenomena of unknown frequency the fluctuating intensity being employed as a time marking.

The invention is illustrated diagrammatically and by way of example by the accompanying drawing in which Figure 1 is partly a side-view of, and partly an axial section through, an arrangement designed according to this invention, and Figure 2 is a similar representation showing a modification.

In both figures l denotes the diaphragm, 2 an insulating body and 3 the glow-cathode. In the example shown in Fig. 1 the voltage of the space-charging diaphragm with respect to the cathode 2 is attained with the aid of the drop of potential along the cathode heater or filament.

In Fig. 2 the aperture of the diaphragm is surrounded with a thick-wire coil 4 through which the heating current passes. The cathode and the diaphragm may have any other suitable shape than that shown on the drawing merely by way of example, and especially the diaphragm need not, by necessity, have conical shape. Furthermore, the insulating body need not necessarily be shoved upon the cathode since under certain circumstances the space charge diaphragm can be independently supported by appropriate support means,

I claim:

1. A high vacuum electron discharge tube comprising an electron emitter, electrical resistance means adapted to supply heat to the emitter, an electrode positioned adjacent the emitter and. means whereby the potential drop along said resistance may be utilized, to maintain said electrode at a potential slightly positive with respect to the emitter whereby the negative space charge caused by electrons leaving the emitter may be compensated.

2. A high vacuum electron discharge tube comprising an electron emitter, electrical resistance means adapted to supply heat to the emitter, an electrode, insulating means for positioning the electrode adjacent the emitter and means whereby the potential drop along said resistance may be utilized to maintain said electrode slightly positive with respect to the emitter in order to compensate the negative space charge caused by electrons leaving the emitter.

3. A high vacuum electron discharge tube comprising an electron emitter, resistance means adapted to be electrically heated by direct current to supply heat to said emitter, an electrode positioned adjacent the emitter, means to connect said emitter to the negative terminal of said resistance, and means to connect said electrode to the positive terminal of said resistance to maintainsaid electrode positive with respect to said emitter whereby the negative space charge, caused by electrons leaving the emitter will be drop along said resistance whereby the negative I space charge caused by electrons leaving the emitter will be compensated.

5. A cathode ray tube comprising an electron" emitter, aresistance for, supplying heat to the emitter and an electrode, means for connecting one end of said resistance to said emitter, means; I

for connecting the other end of said resistance to said electrode and means adapted to applya positive and negative potential to said electrode and resistance, respectively,'whereby the negative space charge caused by electrons leaving the emitter will be compensated, the electrode being 'maintained positive with respect to, the

emitter by anamount equal to the voltage drop across the resistance.

6. An electron discharge tube comprising an emitter, a resistance for supplying heat to said emitter, a magnetic coil surrounding said emitter and an electrode, means for connecting one end of said resistance to said emitter, means for connecting the other end of said resistance to one end of said coil, means for connecting the other end of said coil to said electrode and means for applying a positive and a negative potential to said electrode and said emitter, respectively, whereby the electrode and its potential relativeto the emitterwill compensate, for the negative space charge caused by electrons leaving the emitter.

"7. An electron discharge tube comprising an emitter, a resistance for supplying heat to said emitter, a magnetic coil surrounding said emitter and an electrode, means for connecting one end of said resistance to said emitter, means for conmeeting the other end'of said resistance'to one I end of said coil, means for connecting the other end of said coil to said electrodeand means for applying a positive and a negative potential to said electrode and said emitter, respectively,

whereby the electrode and its potentialrelative to the emitter will compensate for the negative I spacecharge caused by electrons leaving the emitter and whereby the electrons may be concentrated by the coil, the current carrying capacity of said coil being greater than that of said resistance. I

8. An electron discharge tube comprising an emitter, an electrical resistance for. supplying heat to said emittena magnetic coil surrounding said, emitter and an electrode, means for connectingone end of said resistance to said emitter, means for connecting the other end of said resistance to one end of said coil, means for connecting the other end of said coil .to said electrode, and means for applying a potential to said electrode and emitter, whereby the electrode may assume a potential different from. the potential of the emitter to'compensate for the negative space charge caused by electrons leaving the emitter. T V v v EDWIN TRESCHAU. 

